The inventor of the present invention has been disclosed in Japanese Unexamined Patent Application Publication No. H10-122914 (U.S. Pat. No. 5,945,606), which is an elastic member for attaching a sensor device having a protruded portion in a through hole of a sensor attachment member by attaching one-touch operation.
As illustrated in FIG. 5A, the elastic member 1 for attaching a sensor device 2 has therein a hollow portion 40 for attaching a sensor protrusion portion 3 of the sensor device 2. The elastic member 1 is formed by integrally molding of a fore end portion 6 having a fore end protrusion 9 and a fore end flange 10, an intermediate portion 7 including a tapered portion 13 which covers part of the sensor protrusion portion 3 and an intermediate protrusion 14, and a rear end portion 8 having a rear end flange 17. The elastic member 1 for attaching the sensor device 2 is temporarily assembled onto the sensor protrusion portion 3 of the sensor device 2 and inserted into a through hole 5 of a sensor attachment member 4. After the fore end flange 10 is passed through the through hole 5, as illustrated in FIG. 5B, the fore end flange 10 and the rear end flange 17 is locked on the open end peripheral portion of the through hole 5 so that the fore end protrusion 9 is engaged with a concavity 16 of the sensor protrusion portion 3. Thus, the sensor device 2 is thereby firmly attached to the sensor attachment member 4.
However, if the intermediate portion 7 of the elastic member 1 for attaching the sensor device 2 is so formed that the length of the intermediate portion 7 in contact with the inner circumferential surface of the through hole 5 is equal to the upper limit value of tolerance, a gap is produced between the sensor attachment member 4 and the elastic member 1, as illustrated in FIG. 5D. If vibration is applied with the gap present as described above, the elastic member 1 for attaching the sensor device 2 is also vibrated. Therefore, wear, cracking, or the like may be produced in the elastic member 1, so that the sensor device 2 drops off.
Further, if the through hole 5 of the sensor attachment member 4 is so formed that the diameter of the through hole 5 is equal to the lower limit value of tolerance, as illustrated in FIG. 5C, the fore end protrusion 9 of the elastic member 1 for attaching the sensor device 2 does not go back to the concavity 16 of the sensor protrusion portion 3. Therefore, the required holding power for holding the sensor device 2 cannot be obtained, so that the sensor device 2 may drop off.